A number of different focus point detectors have been proposed in the art. Although they are different in the focus point detecting method employed, in most of these focus point detectors, the output signal becomes a maximum when the focus point is detected.
The present invention relates to an automatic focusing camera utilizing such a focus point detector. The invention can be effectively applied to single-lens still cameras, movie cameras and television cameras utilizing interchangeable lenses. That is, according to the invention, various interchangeable lenses having different focal lengths can be used as automatic focusing interchangeable lenses with an interchangeable lens type camera without lowering the lens interchangeability which is essential so that it is not necessary to supply a new camera body with each lens.
An automatic focusing camera in which the driving of the focus control member of the interchangeable lens is governed by a focusing electric motor provided on the camera body has been disclosed by Japanese Patent Application No. 1927/1979 filed by the present applicant which is mentioned here not as prior art but merely as a related device to aid in the understanding of the present invention. In an automatic focusing camera of this type, automatic focalization is achieved by providing a drive transmitting mechanism for the focus control member on the interchangeable lens. With this camera, it is unnecessary to provide an electric motor and a battery in the interchangeable lens. Thus, the automatic focusing camera is simple in construction and low in manufacturing cost. Accordingly, even if a variety of interchangeable lenses are modified so as to be used with the camera, only slight economical burden is put on the user and, accordingly, the user may use any of the interchangeable lenses thus modified. However, since the motor and battery are furnished in the camera body, its output and capacity are necessarily limited. Furthermore, in the case where large interchangeable lenses such as telephoto or super-telephoto interchangeable lenses are modified to automatic focusing interchangeable lenses, the load on the motor increases excessively which may present difficulties in that the service lives of the relevant elements are reduced, the focusing speed may be unsatisfactory, and so forth.
Accordingly, an object of this invention is to eliminate all of the above-described difficulties. According to the invention, all of the photographing lenses can be sufficiently modified to photographing lenses for an automatic focusing camera which are satisfactory from a practical standpoint.